microblaze: Wire up dts configuration

    - enable OF control and embedded OF
    - set default device tree file name to 'microblaze'
    - add CPP to dtc proxy: board/xilinx/dts/microblaze.dts
    - add an empty but processable dts for microblaze-generic

Signed-off-by: Stephan Linz <linz@li-pro.net>
diff --git a/board/xilinx/dts/microblaze.dts b/board/xilinx/dts/microblaze.dts
new file mode 100644
index 0000000..bf984b0
--- /dev/null
+++ b/board/xilinx/dts/microblaze.dts
@@ -0,0 +1 @@
+/include/ BOARD_DTS